Calibration of optical computing devices using traceable filters

Abstract

Calibration of optical computing devices is achieved using mapping functions that map real detector responses to simulated detector responses which are simulated using high-resolution spectra of traceable optical filters and optical computing device characteristics.

What is claimed is: 
     
       1. A method, comprising:
 obtaining reference spectra of two or more optical filters, 
 wherein obtaining the reference spectra comprises using the reference spectra to simulate detector responses of the optical filters, 
 wherein the optical filters have different transmission levels and the reference spectra each have defined spectral patterns that simulate spectral data of a sample; and 
 using the reference spectra to calibrate an optical computing device, wherein using the reference spectra to calibrate the optical computing device comprises:
 obtaining real detector responses of the optical filters; 
 generating a mapping function which maps the simulated detector responses to the real detector responses; and 
 using the mapping function to calibrate measurements of the optical computing device. 
 
 
     
     
       2. The method as defined in  claim 1 , wherein obtaining the reference spectra comprises obtaining the reference spectra using a laboratory spectroscopic instrument. 
     
     
       3. The method as defined in  claim 1 , wherein the reference spectra are used to generate a univariate mapping function. 
     
     
       4. The method as defined in  claim 1 , wherein the reference spectra are used to generate a multivariate mapping function. 
     
     
       5. The method as defined in  claim 1 , wherein obtaining the real detector responses comprises:
 optically interacting electromagnetic radiation the optical filters to produce first optically-interacted lights which correspond to the defined spectral patterns of the reference spectra; 
 optically interacting the optically-interacted lights with one or more Integrated Computational Element (“ICE”) structures to produce second optically-interacted lights which correspond to one or more characteristics of the sample; 
 generating output signals that correspond to the second optically-interacted lights using a detector; and 
 using the output signals to generate the real detector responses. 
 
     
     
       6. The method as defined in  claim 1 , wherein the calibration is performed using optical filters external to the optical computing device. 
     
     
       7. The method as defined in  claim 1 , wherein the calibration is performed using optical filters forming part of the optical computing device. 
     
     
       8. The method as defined in  claim 7 , wherein the calibration comprises moving the optical filters into a path of electromagnetic radiation using a moveable assembly. 
     
     
       9. The method as defined in  claim 8 , wherein the calibration further comprises removing the sample from the path of the electromagnetic radiation. 
     
     
       10. The method as defined in  claim 8 , further comprising:
 after the calibration is performed, moving the optical filters out of the path of the electromagnetic radiation; 
 optically interacting the electromagnetic radiation with the sample to produce sample-interacted light; 
 optically interacting the sample-interacted light with an Integrated Computational Element (“ICE”) structure to produce optically-interacted light which corresponds to a characteristic of the sample; 
 generating an output signal that corresponds to the optically-interacted light using a detector; and 
 using the output signal to determine the characteristic of the sample. 
 
     
     
       11. The method as defined in  claim 8 , further comprising, after the calibration is performed, using the optical filters to govern an intensity of the electromagnetic radiation. 
     
     
       12. The method as defined in  claim 1 , wherein the calibration is performed downhole. 
     
     
       13. An optical computing device, comprising:
 electromagnetic radiation which optically interacts with two or more optical filters to produce first optically-interacted lights having defined spectral patterns that simulate spectral data of a sample; 
 one or more Integrated Computational Element (“ICE”) structures positioned to optically interact with the first optically-interacted lights to produce second optically-interacted lights which correspond to one or more characteristics of the sample; and 
 a detector positioned to detect the second optically-interacted lights and generate output signals used to calibrate the optical computing device. 
 
     
     
       14. The optical computing device as defined in  claim 13 , wherein the optical filters are configured to calibrate the optical computing device. 
     
     
       15. The optical computing device as defined in  claim 13 , further comprising a moveable assembly upon which the optical filters are positioned. 
     
     
       16. The optical computing device as defined in  claim 15 , wherein the moveable assembly is a rotating carousel or a linear array. 
     
     
       17. The optical computing device as defined in  claim 15 , wherein the moveable assembly further comprises an open hole. 
     
     
       18. The optical computing device as defined in  claim 13 , wherein the optical filters are neutral density filters or glass. 
     
     
       19. The optical computing device as defined in  claim 13 , wherein the optical computing device forms part of a reservoir interrogation system. 
     
     
       20. An optical computing method, comprising:
 optically interacting electromagnetic radiation with two or more optical filters to produce first optically-interacted lights having defined spectral patterns that simulate spectral data of a sample; 
 optically interacting one or more Integrated Computational Element (“ICE”) structures with the first optically-interacted lights to produce second optically-interacted lights which correspond to one or more characteristics of the sample; and 
 using a detector to detect the second optically-interacted lights and generate output signals used to calibrate the optical computing device. 
 
     
     
       21. The method as defined in  claim 20 , further comprising calibrating the optical computing device using the optical filters. 
     
     
       22. The method as defined in  claim 21 , wherein the calibration is performed using optical filters external to the optical computing device. 
     
     
       23. The method as defined in  claim 21 , wherein the calibration is performed using optical filters forming part of the optical computing device. 
     
     
       24. The method as defined in  claim 21 , wherein the calibration comprises moving the optical filters into a path of electromagnetic radiation using a moveable assembly. 
     
     
       25. The method as defined in  claim 24 , wherein the calibration further comprises removing the sample from the path of the electromagnetic radiation. 
     
     
       26. The method as defined in  claim 20 , wherein the calibration is performed downhole.